1. Field of the Invention
The present invention generally relates to a carriage and an image recording apparatus such as a printer apparatus, a facsimile apparatus, or a copying apparatus, and particularly to such a carriage which allows a position of a recording head to be so adjusted that a recording surface of the head extends parallel to a path along which a recording medium is fed, and an image recording apparatus including such a carriage.
2. Discussion of Related Art
In the above-indicated image recording apparatus, if an actual distance between a recording surface of, e.g., an ink-jet-type recording head including nozzles, and a recording medium is largely deviated from a designed distance, actual positions where inks outputted from the nozzles are applied to the recording medium are also deviated, which leads to lowering the quality of recording of image. This is also true with dot-impact-type recording heads. This problem has been dealt with by a method disclosed by Japanese Patent Publication No. 62-227677 in which a carriage is supported by an eccentric support bar, and a distance between a recording head and a recording medium is adjusted by appropriate rotation of the eccentric support bar. This method has also been employed by an ink-jet-type recording apparatus, such that a carriage carrying an ink-jet recording head is moved as a whole to adjust a distance between the recording head (i.e., a recording surface thereof) and a recording medium.
FIGS. 11A and 11B show a recording portion of a conventional ink-jet recording apparatus. The recording portion includes a guide bar 111; a carriage 110 that can be reciprocated along the guide bar 111; a recording head 115 mounted on the carriage 110; and a platen 125 for supporting a recording medium, P. The recording head 115 includes a nozzle portion 115a including arrays of nozzles 115b arranged in a recording-medium feeding direction, indicated at Y in FIG. 11A, in which the recording medium P is fed, and also arranged in an image-recording direction, indicated at X, in which the head 115 is moved by the carriage 110 to record an image on the medium P. Each array of nozzles arranged in the feeding direction Y output a same color ink; and each array of nozzles arranged in the recording direction X output different color inks. In this recording portion, regarding the recording direction X, a height position (i.e., an inclination) of the guide bar 111 (as seen in a direction perpendicular to the sheet of FIG. 11A) is so adjusted that respective distances between each of opposite ends of the recording head 115 (i.e., the recordings surface thereof) and the recording medium are equal to each other.
Meanwhile, nozzles that output a same color ink can be arranged in an array with a considerably high density, but difficulty to mount, on a recording head, an increased number of drive devices that drive an increased number of nozzles is increased. Therefore, even if nozzles are arranged with a high density so that a high-density recording can be completed at an increased recording speed, e.g., by just one-time movement of the recording head in the recording direction X, a length of the recording head in the feeding direction Y is not increased, i.e., is considerably short.
If the length of the recording head in the feeding direction Y is short, the quality of recording of image is not influenced by inclination of the recording surface (i.e., so-called “nozzle” surface) of the recording head with respect to the feeding direction Y. More specifically described, if the length of the recording head in the feeding direction Y is short, a clearance, G, between the nozzle surface and the recording medium P is free of a problem that a difference of respective clearances, g1 and g2, between each of opposite ends of the nozzle surface and the recording medium P is excessively large. Thus, the quality of recording of image is not adversely influenced, and accordingly it is not needed to adjust the inclination of the nozzle surface with respect to the feeding direction Y
In other words, regarding the inclination of the nozzle surface with respect to the feeding direction Y, the quality of recording of image is maintained by the improved accuracy of dimensions of parts of the recording head.
On the other hand, when recording, in particular, a low-density recording is performed at a higher speed, it is advantageous to use a recording head having an increased number of nozzles arranged at an appropriate regular interval in the feeding direction Y, i.e., a recording head whose length in the feeding direction Y is large. However, for example, in the case where the length of the recording head in the feeding direction Y is doubled, if the difference of respective clearances g1, g2 between each of the upstream and downstream ends of the nozzle surface and the recording medium P is dealt with by the above-described conventional manner, the difference is also doubled. To avoid this problem, it is needed to further improve the accuracy of dimensions of parts of the recording head and more strictly control the manufacturing of those parts. This leads to increasing the overall cost to produce the recording head. There might be an alternative method in which when the recording apparatus is assembled, the guide bar and/or other parts are so adjusted that the nozzle surface extends parallel to the recording medium P. However, this method would require a complicated adjusting and positioning device.